Conventionally, there have been known several kinds of high temperature regenerators for absorption water cooling; and heating machines, for example, Japanese Laid-Open Patent No. H8-193767 discloses a high temperature regenerator for an absorption water cooling and heating machine. Specifically, this high temperature regenerator has such a structure that a large number of solution tubes which communicates the upper and lower parts of a liquid chamber with each other, are arranged, standing close together, in a passage for combustion gas from a burner within the high temperature regenerator. The large number of solution tubes are divided into two groups, that is, two tube banks one of which is located in the vicinity of the burner so as be directly exposed to the flame, and the other one of which is located distant from the burner, and between which a space with no tubes standing close together, is defined. With this arrangement, the temperature of the flame can be lowered by causing the flame to impinge upon the tube bank located in the vicinity of the burner in order to restrain the generation of thermal NOx, thereby it is possible to aim at lowering the emission of NOx.
Alternatively, Japanese Patent Laid-Open H9-42800 proposes a high temperature regenerator in which dilute solution fed by a solution pump flows through a heat-exchanging tube bank located in the vicinity of a burner and having a high heat flux so as to effect forced convection.
However, the solution tubes in the above-mentioned prior art arrangements, all have circular cross-sectional shapes. In a liquid tube type high temperature regenerator using heat-exchanging tubes having circular cross-sectional shapes, liquid and vapor flow in only one vertically upward direction, and accordingly, all tubes exhibits a one-dimensional flow so as to cause boiling and rising streams. Meanwhile, combustion within the tube bank causes combustion gas to have a high temperature therewithin, accordingly, the heat flux of the solution tubes becomes higher. Conventionally, the higher the heat lux of the solution tubes which stand upright and have circular cross-sectional shapes, the larger the volume of produced vapors within the tubes, the flowing resistance is increased, and as a result, the circulating volume of the solution itself is reduced so that the concentration of the solution becomes locally higher at the heat-transfer surface. Thus, it has been found that the heat-transfer surface is corroded and deteriorated.
That is, if the heat flux of the solution tubes is high, the temperature of the walls of the solution tubes becomes high, and accordingly, the concentration of the solution at the heat-transfer surface becomes locally higher so as to corrode and deteriorate the heat-transfer surface. Thus, since inexpensive materials cannot be used for the solution tubes, the high temperature regenerator is extremely expensive.
Further, the arrangement as proposed by the Japanese Laid-Open Patent No. H9-42800 in which dilute solution from the solution pump flows through the heat-transfer tube bank so as to effect forced convection, is not preferable since the circulation volume of the solution in the high temperature regenerator is, in general, throttled during partial load operation of an absorption refrigerating machine but the high temperature regenerator with the forced convection cannot be operated in a partial load condition.
Accordingly, the present invention is devised in view of the above-mentioned disadvantages caused by the above-mentioned prior art, and accordingly, one object of the present invention is to provide a high temperature regenerator for an absorption water cooling and heating machine, which can prevent the concentration of solution liquid from becoming locally higher at heat-transfer surfaces of the high temperature regenerator so as to be inexpensive and to have a long use life, and in which the circulation volume of the solution can be controlled during partial load operation so as to carry out energy saving operation, and to restrain the generation of thermal NOx, thereby it is possible to aim at lowering the emission of NOx.